Fuel and air

P029D — Cylinder 1 Injector Leaking

Severity: medium Drive with care, to a shop

What P029D means

The engine control module has determined that the cylinder 1 fuel injector is leaking or not delivering fuel as commanded. An injector should seal tightly between pulses and spray a precise amount of fuel. A leak lets extra fuel into the cylinder, which enriches the mixture and makes the engine run unevenly.

Symptoms

  • Check engine light on
  • Rough idle
  • Cylinder 1 misfire
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Fuel smell in the engine bay or from the exhaust
  • Hard starting when hot

Possible causes

  1. Leaking or sticking cylinder 1 injector
  2. Worn injector seals or a damaged injector body
  3. Corroded terminals, open or shorted injector wiring
  4. Excessive fuel rail pressure (regulator or pump fault)
  5. Faulty oxygen sensor skewing fuel trim
  6. Intake air leak shifting the mixture
  7. Rarely, ECM software fault or failure

How to diagnose

  1. Scan all codes and freeze frame data, noting any other mixture or misfire codes
  2. Review short-term and long-term fuel trims and cylinder balance
  3. Inspect the cylinder 1 injector connector and harness, including ground
  4. Measure injector resistance and check the drive signal with a scope or noid light
  5. Test fuel pressure and its ability to hold after shutdown
  6. Pull the cylinder 1 spark plug and look for fuel wetting or heavy soot
  7. Check the intake and exhaust for leaks
  8. Swap the injector with a neighbor and see if the fault follows it

Common fixes

  • Replace or service the cylinder 1 injector with new seals
  • Repair the injector wiring or connector
  • Replace a faulty oxygen sensor or fuel pressure regulator
  • Change engine oil if it is diluted with fuel
  • Update ECM software or replace the ECM (rare)

Questions and answers

What does P029D mean?

The ECM believes the cylinder 1 injector is leaking or malfunctioning. The air-fuel mixture in that cylinder then differs from what it expects, and the engine may misfire.

Can I drive with code P029D?

Only for a short trip to get it repaired. Extended driving risks diluted oil, overheating, and a damaged catalytic converter.

Do I always need a new injector?

No. Check the wiring, connector, fuel pressure, and for air leaks first. If the injector itself is at fault, it is replaced or serviced.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.